This invention relates to a front fork for a motor cycle. In particular, it relates to a front fork which sharply increases a damping force in proximity to a maximum compression stroke.
A front fork is such that a tube connected to the vehicle wheels is inserted to slide freely in a tube connected to the vehicle body. These tubes undergo compression or extension operations relative to one another due to vibrations input to the motor cycle.
A front fork as disclosed for example in JP-A7-174179 or JP-A10-103399 generates a strong damping force in proximity to maximum compression during a compression stroke in order to prevent the compressed tubes from colliding with one another.
However this type of front fork may produce a shock since an excessively strong damping force is rapidly produced in proximity to maximum compression. When such a shock is transmitted from the front fork to the vehicle body, the rider receives an unpleasant sensation and thus riding comfort is adversely affected.
It is therefore an object of this invention to provide a front fork which improves riding comfort by preventing the generation of a shock by gradually increasing the damping force in proximity to maximum compression of a front fork.
In order to achieve above the object the invention provides a front fork for a motor cycle which comprises a tube connected to a vehicle body; a tube connected to a vehicle-wheel and engaging to slide freely with respect to the vehicle-body tube; a damper disposed in an interior space between the vehicle-body tube and the vehicle-wheel tube, the damper extending or compressing in response to extension or compression of the tubes; a suspension spring disposed in the interior space between the vehicle-body tube and the vehicle-wheel tube, the suspension spring biased in a direction extending the tubes; a first gas chamber formed in the interior space, and an oil chamber positioned above the first gas chamber and introducing oil from the damper, the oil surface in the oil chamber varying as a result of the compression stroke position of the front fork; a second gas chamber formed in the interior space and connected to the first gas chamber through a orifice; a space A formed between the outer periphery of the suspension spring and the inner periphery of the vehicle-body tube, the space A being closed by enter of the tip of the vehicle-wheel tube, and when the space A is open, oil in the oil chamber flows through the space A; and a hole provided in the first gas chamber, and allowing flow of all oil after the space A is closed.
The details as well as other features and advantages of the invention are set forth in the remainder of the specification and are shown in the accompanying drawings.